Camshaft phasers for varying the timing of valves in internal combustion engines are well known. A typical phaser comprises a rotor, attached to a camshaft, and a stator surrounding the rotor and driven in time with an engine crankshaft. The phaser is able to vary the angular position of the rotor with respect to the stator and thus to vary the valve timing imposed on the camshaft with respect to the crankshaft and pistons.
A phaser also typically includes an external timing wheel having notches, tabs, or other indicia, and being fixedly attached to the rotor such that the angular position of the rotor within the stator may be determined at any time by interrogating the target wheel. A target wheel also typically includes means for anchoring an end of a rotor bias spring.
A prior art target wheel typically is formed by powdered metal (PM) technology, which can add significant mass, and thus inertia, to a rotor assembly, whereas it is desirable that the target wheel be of very low mass to increase speed of response of the phaser. PM is also a relatively expensive means for forming a relatively simple component.
What is need in the art is an inexpensive, low-mass timing wheel for a camshaft phaser.
It is a principal object of the present invention to reduce the rotational mass and cost of a camshaft phaser.